In many industries the application of microwave and plasma technology already made it possible to develop processes which are consuming less resources, helping to save energy and are producing less toxic waste. However, these technologies can also be used to manage and treat our waste directly, for example by recycling valuable raw materials, conserving energy or neutralising hazardous substances and micro-organisms. Some typical applications in the field of waste management include:
Waste tyres are one of the largest and most problematic sources of waste, due to two reasons: Firstly, almost everybody of us is producing waste tyres, whether directly or indirectly, and secondly, tyres are designed for durability, which also means that they will not decompose or otherwise degrade. While a limited number of tyres are already undergoing recycling in one way or the other, e.g. being reused as retreaded tyres, being shredded into "crumb rubber" which can be used for elastic pavements or a filler for asphalt, or being burned in cement factories as a source of energy, the majority of waste tyres nowadays are still ending up in landfills. However, microwave energy offers two ways of reusing these tyres, namely devulcanisation and pyrolysis:
Devulcanisation is the reversal of the vulcanisation process taking place during the manufacturing of the tyres or other rubber products. With modern devulcanisation methods it is possible to break up the cross-links of the elastomers without degrading the compounds or generating any pollution. The devulcanised rubber can then be blended with fresh compounds to form a mixture that performs as well as completely fresh compounds, but with a high content of recycled rubber, thus saving valuable resources.
Pyrolysis is the thermal decomposition of rubber or any other organic compound. When heated up in an oxygen-free atmosphere, the rubber contained in the tyre will decompose into liquid and gaseous carbon-hydrogens which are constantly removed, while the mineral fillers, carbon black and metal parts remain in the process chamber and, after a simple mechanical separation step, can be recycled. The carbon-hydrogens released by the pyrolysis can be used as fuel to generate heat or electrical energy. Because tyres have a high content of carbon black and readily absorb microwave energy, this is a very clean, efficient, fast and energy saving way of performing the pyrolysis.
Many industrial sludges are containing hazardous substances and must therefore be disposed a hazardous waste, which is expensive and calculated based on the weight of the sludge to be disposed. Microwave dryers are a fast and cost-efficient solution to reduce the weight of the sludge and therefore help to save a considerable amount of disposal cost.
Solvents like toluene, xylene and others are widely used in the automotive and other industries and find their way into waste and sludges from these factories. Because they are hazardous to our health they must be prevented from entering our environment, which means that waste containing them must be disposed as hazardous waste. However, with the application of microwave based systems it is possible to recover these solvents from the waste, saving not only money by reusing the solvents, but also cutting down on disposal cost for hazardous waste.
Filter ashes from power plants and incinerators, waste from the processing of radioactive substances or dried sludge from chemical factories and other manufacturing processes can contain a high amount of toxic substances and are therefore subject to stringent regulations with regards to storage and disposal. One of the safest ways to dispose these wastes is to apply the process of vitrification, whereby the waste is first mixed with certain chemical compounds like sodium carbonate, calcium oxide, or silicon dioxide and then exposed to temperatures of around 1000 °C. At this temperature, the mixture of waste and chemicals starts to melt down and form a glass, which after cooling / solidification effectively encapsulates the hazardous substances, even when exposed to groundwater. Another advantage is the strongly reduced storage volume, as vitrification of solid waste can reduce its volume by up to 80 %. Microwave energy is especially well suited to heat up the mixture in a fast and efficient way.
Medical waste can contain high amounts of pathogenic bacteria and viruses, for a safe disposal it is therefore required to neutralise these organisms. Microwave systems are ideally suited for this purpose as they are not only very efficient in neutralising bacteria, viruses and other micro-organisms, but depending on the waste at hand they also offer the option to either pyrolyse or vitrify the waste in a one-step operation, reducing its volume and making it absolutely safe for disposal.
Electronic waste not only poses a danger due to the content of hazardous substances like lead, but also contains a high amount of precious metals like silver, gold etc. Microwave technology does not only make it possible to reclaim these precious metals, but at the same time vitrify the remaining compounds, leading to a considerable reduction in volume and ensure that hazardous substances are safely encapsulated and cannot leach into the environment.
For more information about the usage of microwave technology for waste management contact us.